The Inline Storage System Pump Station (ISSPS) is one of Milwaukee Metropolitan Sewerage District’s (MMSD) most critical pieces of infrastructure. The Inline Storage System (ISS) is a 30-foot diameter, deep conveyance tunnel at the heart of a network of sanitary and combined sewers used by MMSD. The ISS captures and conveys wet weather flow to the ISSPS to minimize overflows into Lake Michigan and flooding in the greater Milwaukee area. 

Located 350 feet below the surface at the Jones Island Water Reclamation Facility, the ISSPS is a single-cavern pump station that houses three dry-pit, split-case centrifugal pumps. These pumps are used to dewater the tunnel, directing wet weather flows to either or both of MMSD’s existing water reclamation facilities. 

The purpose of the project is to increase MMSD’s pumping capacity and improve the reliability of the three, 20-year-old pumps. MMSD retained Black & Veatch to provide engineering services for preliminary evaluations, design, equipment procurement, construction and startup phases of the ISSPS upgrades project.

Black & Veatch analysis showed that the desired pumping capacity increase could be achieved without increasing the physical size of the underground pump station or building a new station, which was originally perceived as the only way to accomplish the project’s goal.

One key project constraint was that the full ISSPS pumping capacity needed to be maintained throughout construction. The only exception to this constraint was during a six-week period each winter when historical inflows are typically low.

Black & Veatch’s solution was to procure key pieces of equipment as much in advance as possible, so that they would be on site and ready when needed. The construction contract was written around three six-week periods, during which one of the three pumps could be taken out of service for repair and recommissioning, including all startup, testing and training activities.